Decision between transcription elongation and intrinsic termination plays a crucial role in regulation of gene expression in bacteria. Classical examples of such regulation include attenuation mechanisms of amino acid biosynthetic operons in Escherichia coll. In those and most other cases the effector has been found to be a protein that either positively or negatively influenced intrinsic termination by directly affecting folding of the terminator stem-loop structure or affecting the formation of an alternate structure that competes with the stem-loop of the terminator. Recent work from this group describes a novel transcription attenuation mechanism, which controls riboflavin synthesis in Bacillus subtilis. This mechanism is unusual because small molecules, FMN and FAD, play a role of the effector that bind to the leader nascent transcript directly, changes its structure, and activate premature intrinsic termination. The long-term objective of the proposed work is to characterize in detail several biosynthetic operons in B. subtilis, which regulation resembles that of "riboflavin" pattern, i.e. the situation where sensing a small molecule by nascent RNA controls gene expression. Specific aims of this proposal are: 1.Complete studies on the transcription regulation of the riboflavin operon in B. subtilis. Genetic and biochemical experiments are proposed to address the role of a leader peptide in controlling the transcription of the riboflavin operon from B. subtilis. 2. Determine the mechanism of the transcription regulation of the thiamin operon in B. subtilis Genetic and biochemical experiments are proposed to elucidate the structure and function of the leader regulatory region of the thiamin operon from B. subtilis. 3. Determine the mechanism of the transcription regulation of the S-box regulon in B. subtilis Genetic and biochemical experiments are proposed to elucidate the structure and function of the leader regulatory region of the methionine operon from B. subtilis. This research will be done mainly in Moscow, Russia at the State Research Institute of Genetics and Selection of Industrial Microorganisms in collaboration with Dr. Alexander Mironov as an extension of the NIH grant # R01GM58750.